Hi,

My question is two-fold.

(i) I have a URDF which has parallel linkages and multijoint definitions. I noticed that having a child link with multiple parent links gave unexpected behavior when using the joint_state_publisher gui to move the joints: I could only use one actuator joint to move the head I am trying to control. The xacro file is in this link.

(ii) I tried to export my URDF model to gazebo and in light of this, I wrote a separate file as was done in the rrbot example that adds a gazebo element for each link and joint. So I include the superchick_gazebo file within my superchick.xacro file and when I try to load it in gazebo, I notice that all my links come out correctly but the joints are not well placed as they are in rVIZ :

Here's what the interpreted sdf looked like in Gazebo.

In my terminal, I noticed warnings such as

Warning [parser_urdf.cc:346] attempted to add visual to link [base_panel], but it already exists under group [lump::panel_12_oc]
Warning [parser_urdf.cc:346] attempted to add visual to link [base_panel], but it already exists under group [lump::panel_3_oc]
Warning [parser_urdf.cc:346] attempted to add visual to link [base_panel], but it already exists under group [lump::panel_9_oc]
Warning [parser_urdf.cc:317] attempted to add collision to link [base_panel], but it already exists under group [lump::panel_12_oc]
Warning [parser_urdf.cc:317] attempted to add collision to link [base_panel], but it already exists under group [lump::panel_3_oc]
Warning [parser_urdf.cc:317] attempted to add collision to link [base_panel], but it already exists under group [lump::panel_9_oc]
Warning [parser_urdf.cc:346] attempted to add visual to link [table_top], but it already exists under group [lump::base_panel]
Warning [parser_urdf.cc:346] attempted to add visual to link [table_top], but it already exists under group [lump::panel_12_oc]
Warning [parser_urdf.cc:346] attempted to add visual to link [table_top], but it already exists under group [lump::panel_3_oc]
Warning [parser_urdf.cc:346] attempted to add visual to link [table_top], but it already exists under group [lump::panel_9_oc]
Warning [parser_urdf.cc:317] attempted to add collision to link [table_top], but it already exists under group [lump::base_panel]
Warning [parser_urdf.cc:317] attempted to add collision to link [table_top], but it already exists under group [lump::panel_12_oc]
Warning [parser_urdf.cc:317] attempted to add collision to link [table_top], but it already exists under group [lump::panel_3_oc]
Warning [parser_urdf.cc:317] attempted to add collision to link [table_top], but it already exists under group [lump::panel_9_oc]
Warning [parser_urdf.cc:346] attempted to add visual to link [table_top], but it already exists under group [lump::big_bladder_link]
Warning [parser_urdf.cc:317] attempted to add collision to link [table_top], but it already exists under group [lump::big_bladder_link]
Warning [parser_urdf.cc:346] attempted to add visual to link [table_top], but it already exists under group [lump::left_bladder]
Warning [parser_urdf.cc:317] attempted to add collision to link [table_top], but it already exists under group [lump::left_bladder]
Warning [parser_urdf.cc:346] attempted to add visual to link [table_top], but it already exists under group [lump::right_bladder]
Warning [parser_urdf.cc:317] attempted to add collision to link [table_top], but it already exists under group [lump::right_bladder]
Warning [parser_urdf.cc:346] attempted to add visual to link [table_top], but it already exists under group [lump::table_cover]
Warning [parser_urdf.cc:317] attempted to add collision to link [table_top], but it already exists under group [lump::table_cover]
Warning [parser_urdf.cc:346] attempted to add visual to link [right_leg], but it already exists under group [lump::table_top]
Warning [parser_urdf.cc:346] attempted to add visual to link [right_leg], but it already exists under group [lump::base_panel]
Warning [parser_urdf.cc:346] attempted to add visual to link [right_leg], but it already exists under group [lump::big_bladder_link]
Warning [parser_urdf.cc:346] attempted to add visual to link [right_leg], but it already exists under group [lump::left_bladder]
Warning [parser_urdf.cc:346] attempted to add visual to link [right_leg], but it already exists under group [lump::panel_12_oc]
Warning [parser_urdf.cc:346] attempted to add visual to link [right_leg], but it already exists under group [lump::panel_3_oc]
Warning [parser_urdf.cc:346] attempted to add visual to link [right_leg], but it already exists under group [lump::panel_9_oc]
Warning [parser_urdf.cc:346] attempted to add visual to link [right_leg], but it already exists under group [lump::right_bladder]
Warning [parser_urdf.cc:346] attempted to add visual to link [right_leg], but it already exists under group [lump::table_cover]
Warning [parser_urdf.cc:317] attempted to add collision to link [right_leg], but it already exists under group [lump::table_top]
Warning [parser_urdf.cc:317] attempted to add collision to link [right_leg], but it already exists under group [lump::base_panel]
Warning [parser_urdf.cc:317] attempted to add collision to link [right_leg], but it already exists under group [lump::big_bladder_link]
Warning [parser_urdf.cc:317] attempted to add collision to link [right_leg], but it already exists under group [lump::left_bladder]
Warning [parser_urdf.cc:317] attempted to add collision to link [right_leg], but it already exists under group [lump::panel_12_oc]
Warning [parser_urdf.cc:317] attempted to add collision to link [right_leg], but it already exists under group [lump::panel_3_oc]
Warning [parser_urdf.cc:317] attempted to add collision to link [right_leg], but it already exists under group [lump::panel_9_oc]
Warning [parser_urdf.cc:317] attempted to add collision to link [right_leg], but it already exists under group [lump::right_bladder]
Warning [parser_urdf.cc:317] attempted to add collision to link [right_leg], but it already exists under group [lump::table_cover]
Error [Model.cc:640] can't have two joint with the same name
Exception [Model.cc:641] can't have two joint with the same name

Error [Model.cc:134] LoadJoint Failed
[INFO] [WallTime: 1479666240.902647] Spawn status: SpawnModel: Successfully spawned model
[urdf_spawner-4] process has finished cleanly
log file: /home/lex/.ros/log/817283fc-af4e-11e6-8627-801934199d44/urdf_spawner-4*.log

Msg Connected to gazebo master @ http://127.0.0.1:11345
Msg Publicized address: 10.0.0.3
Error [Plugin.hh:156] Failed to load plugin libgazebo_ros_control.so: libgazebo_ros_control.so: cannot open shared object file: No such file or directory

I checked my URDF over and over to be sure that no two joints have the same name but every time I do

bash gzsdf print superchick.urdf > superchick.sdf

I notice there are two joints automatically generated for certain joints.

As a workaround, I think if there is a way to call a clean sdf directly in gazebo, that would be nice. I looked online, there doesn't seem to be a nice tutorial on how this can be achieved.

Are there ways to mitigate this problem?